capacitor problems

i have a 1.2 farad capacitor, and when i try to charge it, it charges up to 10.x volts than it just stops charging.  i tried to discharge it and try charging it again, but it did the same thing.  i thought it would be my car so i tried one of my other cars to charge it and it did the same thing.

i used a resitor the first time, than switched to a test light the next few times.....both unsuccessful.  the cap is grounded to the chassis and it is a good ground.......dont know what i'm doing wrong....

help please.....

DYohn] wrote:

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capacitor will equalize at whatever system voltage is.  If a capacitor is connected between the battery + and ground, it will charge to the same voltage as the battery.  It is impossible for it do do otherwise.  Where are you reading this "10.x" volts?  Using what meter?  Is the car running?

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what i'm saying is that when you buy a cap the first thing you have to do is charge is, correct?

well, when i tried to charge is with the engine off, it would only go up to 10.x volts, it wouldn't reach the 12.5 volts that the car battery was.  i used a dmm to measure the cap and battery.

the same as the cap.  the cap has one of those digital voltmeters on them....would that be a problem......

i never experienced this before, but when the cap tops at at around 10 volts, i remove the resistor and connect all the wires for the cap, but by the time i do all that the cap loses all its power?

robfontelera wrote:

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the same as the cap.  the cap has one of those digital voltmeters on them....would that be a problem......i never experienced this before, but when the cap tops at at around 10 volts, i remove the resistor and connect all the wires for the cap, but by the time i do all that the cap loses all its power?

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It is defective if it "loses all its power" as soon as it is disconnected.  But don't trust anything a cheap digital "voltmeter" on a cap tells you. 

Why do you think you need a cap anyway?

Also, what does your battery voltage read with a DMM and the cap out of the circuit?

i have dimming probs when i turn up the volume.  my battery reads 12.4 volts when the engine is off.  it's a new battery.

would you know if i redid all the grounds in the engine bay, and maybe even ground the block to the body if that would help?

wheelerdr wrote:

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i would go to a local parts store like napa and have you battery and alt tested. you can also try getting a yellow top deep cycle battery this will help all around.

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do you think if i added more grounds in the engine bay it would help?  like grounding the motor to the body or chassis, run new grounds from the battery to chassis, to the alternator, to the body?

i was thinking about buying a yellow top battery, but someone advised me to try regrounding everything first.

robupnya wrote:

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now that i didn't know.  well, i have a 1998 toyota corolla, don't know what the alternator is rated at.  i am running a kenwood 800 w amp powering a single 12" rockford fosgate hx2 sub.

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There is no way you need a capacitor.  If your lights are dimming with 800 watts (kenwood makes an 800 watt amplifier?) then you have alternator and/or battery issues.

Yeah... Here is my electrical power supply setup:

105 amp alternator(f**k alterstart and their ubey gheyness)
Standard engine battery from Napa
Then a Yellow Top in the trunk wired from the front battery
Amp is wired off the yellow top

I have a volt autometer in my car for a nice idea of how the system is holding up. I haven't dropped under 12 volts and only hit 12 volts when the car is off or at idle. When running it holds 13.5-14.2 depending on its mood mostly. I am pushing something like 1300wRMS plus the beastly heater/ac system in the car likes to suck it up as well. The only problem I have is that rattling on the plastic, but that has nothing to do with power. :)

If you are dimming at that, look into a more powerful alternator or a replacement.

(BTW your alt is 80 amp, so an upgrade might not be a bad idea?)

are alternators easy to install?

would i need a specific model, or do all alternators fit in any car?

i got the car from my mom about 2 months ago cause she bought a new solara, so everything in it right now is 7 yrs. old.....1998.  i was also thinking, since the car came from daly city, ca....very foggy weather everyday, there can be some rust where all the ground points are right now, that's the reason i was asking bout if i regrounded everything if that would make a difference.

thanks for the info